Methods of forming a masking pattern for integrated circuits

ABSTRACT

In some embodiments, methods for forming a masking pattern for an integrated circuit are disclosed. In one embodiment, mandrels defining a first pattern are formed in a first masking layer over a target layer. A second masking layer is deposited to at least partially fill spaces of the first pattern. Sacrificial structures are formed between the mandrels and the second masking layer. After depositing the second masking layer and forming the sacrificial structures, the sacrificial structures are removed to define gaps between the mandrels and the second masking layer, thereby defining a second pattern. The second pattern includes at least parts of the mandrels and intervening mask features alternating with the mandrels. The second pattern may be transferred into the target layer. In some embodiments, the method allows the formation of features having a high density and a small pitch while also allowing the formation of features having various shapes and sizes.

CLAIM FOR PRIORITY

This application is a continuation of U.S. patent application Ser. No.12/546,466, filed Aug. 24, 2009, entitled METHODS OF FORMING A MASKINGPATTERN FOR INTEGRATED CIRCUITS, which claims the priority benefit under35 U.S.C. §119(e) of Provisional Application Ser. No. 61/117,526, filedNov. 24, 2008. The full disclosures of the priority application areincorporated herein by reference.

BACKGROUND

1. Field of the Invention

This invention relates generally to integrated circuit fabrication and,more particularly, to masking techniques.

2. Description of the Related Art

As a consequence of many factors, including demand for increasedportability, computing power, memory capacity and energy efficiency,integrated circuits are continuously being made more dense. The sizes ofthe constituent features that form the integrated circuits, e.g.,electrical devices and interconnect lines, are constantly beingdecreased to facilitate this scaling.

The trend of decreasing feature size is evident, for example, in memorycircuits or devices such as dynamic random access memories (DRAMs),flash memory, static random access memories (SRAMs), ferroelectric (FE)memories, etc. To take one example, DRAM typically comprises millions ofidentical circuit elements, known as memory cells. In general, acapacitor-based memory cell, such as in conventional DRAM, typicallyconsists of two electrical devices: a storage capacitor and an accessfield effect transistor. Each memory cell is an addressable locationthat can store one bit (binary digit) of data. A bit can be written to acell through the transistor and can be read by sensing charge in thecapacitor. Some memory technologies employ elements that can act as botha storage device and a switch (e.g., dendritic memory employingsilver-doped chalcogenide glass) and some nonvolatile memories do notrequire switches for each cell (e.g., magnetoresistive RAM). Inaddition, in some technologies, some elements can act as both chargestorage and charge sensing devices. For example, this is the case withflash memory, thus, allowing this type of memory to have one of thesmallest cell sizes (4F²) of all memory technologies. In general, bydecreasing the sizes of the electrical devices that constitute a memorycell and the sizes of the conducting lines that access the memory cells,the memory devices can be made smaller. Additionally, storage capacitiescan be increased by fitting more memory cells on a given area in thememory devices.

The continual reduction in feature sizes places ever greater demands onthe techniques used to form the features. For example, photolithographyis commonly used to pattern features, such as conductive lines. Theconcept of pitch can be used to describe the sizes of these features.Pitch is defined as the distance between an identical point in twoneighboring features when the pattern includes repeating features, as inarrays. These features are typically defined by spaces between adjacentfeatures, which spaces are typically filled by a material, such as aninsulator. As a result, pitch can be viewed as the sum of the width of afeature and of the width of the space on one side of the featureseparating that feature from a neighboring feature. However, due tofactors such as optics and light or radiation wavelength,photolithography techniques each have a minimum pitch below which aparticular photolithographic technique cannot reliably form features.Thus, the minimum pitch of a photolithographic technique is an obstacleto continued feature size reduction.

“Pitch doubling” or “pitch multiplication” is one method for extendingthe capabilities of photolithographic techniques beyond their minimumpitch. A pitch multiplication method is illustrated in FIGS. 1A-1F anddescribed in U.S. Pat. No. 5,328,810, issued to Lowrey et al., theentire disclosure of which is incorporated herein by reference. Withreference to FIG. 1A, a pattern of lines 10 is photolithographicallyformed in a photoresist layer, which overlies a layer 20 of anexpendable material, which in turn overlies a substrate 30. As shown inFIG. 1B, the pattern is then transferred using an etch (for example, ananisotropic etch) to the layer 20, thereby forming placeholders, ormandrels, 40. The photoresist lines 10 can be stripped and the mandrels40 can be isotropically etched to increase the distance betweenneighboring mandrels 40, as shown in FIG. 1C. A layer 50 of spacermaterial is subsequently deposited over the mandrels 40, as shown inFIG. 1D. Spacers 60, i.e., the material extending or originally formedextending from sidewalls of another material, are then formed on thesides of the mandrels 40. The spacer formation is accomplished bypreferentially etching the spacer material from the horizontal surfaces70 and 80 in a directional spacer etch, as shown in FIG. 1E. Theremaining mandrels 40 are then removed, leaving behind only the spacers60, which together act as a mask for patterning, as shown in FIG. 1F.Thus, where a given pitch previously included a pattern defining onefeature and one space, the same width now includes two features and twospaces, with the spaces defined by, e.g., the spacers 60. As a result,the smallest feature size possible with a photolithographic technique iseffectively decreased.

While the pitch is actually halved in the example above, this reductionin pitch is conventionally referred to as pitch “doubling,” or, moregenerally, pitch “multiplication.” Thus, conventionally,“multiplication” of pitch by a certain factor actually involves reducingthe pitch by that factor. The conventional terminology is retainedherein.

Because a spacer pattern typically follows the outlines of mandrels,pitch multiplication is generally useful for forming regularly spacedlinear features, such as conductive interconnect lines in a memoryarray. However, in addition to features which extend linearly overrelatively large distances (e.g., conductive interconnect lines),integrated circuits typically contain features having various shapes andsizes which can be difficult to form by conventional pitchmultiplication processes. In addition, the continuing reduction in thesizes of integrated circuits has provided a continuing demand forreductions in the sizes of features.

Accordingly, there is a continuing need for methods of forming featureshaving a small pitch and high density.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the Detailed Description ofthe Preferred Embodiments and from the appended drawings, which aremeant to illustrate and not to limit certain embodiments of theinvention, and wherein:

FIGS. 1A-1F are schematic, cross-sectional side views showing a sequenceof masking patterns for forming conductive lines, in accordance with aprior art pitch doubling method;

FIGS. 2A and 2B are schematic, cross-sectional views showingintermediate masking structures, in accordance with some embodiments;

FIGS. 3A-3K are schematic, cross-sectional views showing a processsequence for forming features in a target layer, in accordance with someembodiments;

FIGS. 4A-4H are schematic, cross-sectional views showing a processsequence for forming features in a target layer, in accordance withother embodiments;

FIGS. 5A-5D are schematic, cross-sectional views showing a processsequence for forming features in a target layer, in accordance with yetother embodiments;

FIGS. 6A-6E are schematic, cross-sectional views showing a processsequence for forming features in a target layer, in accordance with yetother embodiments;

FIGS. 7A-7F are schematic, cross-sectional views showing a processsequence for forming features in a target layer, in accordance with yetother embodiments;

FIGS. 8A-8E are schematic, cross-sectional views showing a processsequence for forming features in a target layer, in accordance with yetother embodiments;

FIGS. 9A-9D are schematic, cross-sectional views showing a processsequence for forming features in a target layer, using anti-spacers andspacers, in accordance with yet other embodiments;

FIGS. 10A-12B are schematic, top plan views and cross-sectional viewsshowing a process sequence for forming three dimensional features in atarget layer, in accordance with some embodiments, wherein FIGS. 10A,11A, and 12A are schematic, top plan views; FIG. 10B is across-sectional view of FIG. 10A, taken along the line 10B-10B; FIGS.11B and 11C are cross-sectional views of FIG. 11A, taken along the lines11B-11B and 11C-11C, respectively; and FIG. 12B is a cross-sectionalview of FIG. 12A, taken along the line 12B-12B;

FIG. 12C is a schematic perspective view of a structure resulting fromthe process of FIGS. 10A-12B;

FIGS. 13A-15B are schematic, top plan views and cross-sectional viewsshowing a process sequence for forming three dimensional features in atarget layer, in accordance with some embodiments, wherein FIGS. 13A and14A are schematic, top plan views; FIG. 13B is a cross-section of FIG.13A, taken along the line 13B-13B; FIGS. 14B and 14C are cross-sectionalviews of FIG. 14A, taken along the lines 14B-14B and 14C-14C,respectively; and FIGS. 15A and 15B are cross-sectional views of FIG.14A, taken along the lines 14B-14B and 14C-14C, respectively, after apattern of features has been transferred into the target layer;

FIG. 15C is a schematic, perspective view of a structure resulting fromthe process of FIGS. 13A-15B; and

FIGS. 16A-16D are schematic, top plan views showing a process sequencefor forming landing pads, in accordance with some embodiments.

DETAILED DESCRIPTION

In the context of this document, the term “integrated circuit (IC)device” refers to a semiconductor device, including, but not limited to,a memory device and a microprocessor. The memory device may be avolatile memory such as a random access memory (RAM) or non-volatilememory such as a read-only memory (ROM). Examples of RAMs includedynamic random access memories (DRAMs) and static random access memories(SRAMs). Examples of ROMs include programmable read-only memories(PROMs), erasable programmable read-only memories (EPROMs),electrically-erasable programmable read-only memories (EEPROMs), andflash memories.

The term “semiconductor substrate” is defined to mean any constructioncomprising semiconductor materials, including, but not limited to, bulksemiconductor materials such as a semiconductor wafer (either alone orin integrated assemblies comprising other materials thereon) andsemiconductor material layers (either alone or in integrated assembliescomprising other materials). The term “substrate” refers to anysupporting substrate, including, but not limited to, the semiconductorsubstrates described above. Also in the context of this document, theterm “layer” encompasses both the singular and the plural unlessotherwise indicated. A layer may overlie a portion of, or the entiretyof, a substrate.

The term, “features,” as used herein, refers to parts of a pattern, suchas lines, spaces, via, pillars, trenches, troughs, or moats. The term,“mandrels,” as used herein, refers to mask features formed at a verticallevel. The term, “intervening mask features, as used herein, refers tomask features that are formed between two immediately neighboringmandrels.

The term “array” refers to a regularly repeating pattern of IC elementson a semiconductor substrate. For example, a memory array typically hasa number of identical memory cells in a matrix form. Logic arrays maysimilarly include repeating patterns of conductive lines and/ortransistors.

The term, “target layer,” as used herein, refers to a layer in which apattern of features is formed. A target layer may be part of asemiconductor substrate. A target layer may include metal,semiconductor, and/or insulator.

It will also be appreciated that transferring a pattern from a first(e.g., masking) level to a second level involves forming features in thesecond level that generally correspond to features on the first level.For example, the path of lines in the second level will generally followthe path of lines on the first level. The location of other features onthe second level will correspond to the location of similar features onthe first level. The precise shapes and sizes of corresponding featurescan vary from the first level to the second level, however due, forexample, to trim and growth steps. As another example, depending uponetch chemistries and conditions, the sizes of and relative spacingsbetween the features forming the transferred pattern can be enlarged ordiminished relative to the pattern on the first level, while stillresembling the same initial “pattern.”

While “processing” through masks is described for some embodiments asetching to transfer a hard mask pattern into a target layer, the skilledartisan will appreciate that processing in other embodiments cancomprise, e.g., oxidation, nitridation, selective deposition, doping,etc. through the masks.

In some embodiments, methods are provided for forming a masking patternfor an electronic device, such as an integrated circuit. First, mandrelsdefining a first pattern are formed in a first masking layer providedover a target layer. As nonlimiting examples, the mandrels may be formedof a resist, a hard mask material, or part of a substrate. A secondmasking layer is deposited in spaces between the mandrels. The secondmasking layer at least partly fills the spaces between the mandrels. Insome embodiments, the second masking layer may bury the first pattern.

Before or after depositing the second masking layer, one or moresacrificial structures are formed to define a second pattern having asmaller pitch than the first pattern. In some embodiments, the one ormore sacrificial structures may be formed by altering, e.g., chemicallyaltering, portions of either or both of the mandrels and the secondmasking layer. In other embodiments, the one or more sacrificialstructures may be formed by growing or depositing a layer of a materialthat is different, or selectively etchable relative to, those of thefirst and second masking layers before depositing the second maskinglayer. The resulting intermediate masking structures according to someembodiments are shown in FIGS. 2A and 2B.

In FIG. 2A, an intermediate masking structure 200A includes mandrels130, a second masking layer 140, and sacrificial structures 150 that areformed on a target layer 110. The mandrels 130 are spaced apart. Thesacrificial structures 150 are formed on top and side surfaces 130 a,130 b of the mandrels 130. The second masking layer 140 fills theremainder of the spaces between the mandrels 130.

Referring to FIG. 2B, another intermediate masking structure 200Bincludes mandrels 130, a second masking layer 140, sacrificialstructures 150, and partial gap fillers 155 formed on a target layer110. The mandrels 130 are spaced apart from one another on the targetlayer 110. The sacrificial structures 150 are conformally formed on topand side surfaces 130 a, 130 b of the mandrels 130. The partial gapfillers 155 are formed of the same material as the material of thesacrificial structures. The partial gap fillers 155 are formed on topsurfaces 112 of the target layer 110 between the mandrels 130 coveredwith the sacrificial structures 150. In some embodiments, the partialgap fillers 155 may be formed simultaneously with the sacrificialstructures 150. The second masking layer 140 fills the remaining spacesbetween the mandrels 130.

The sacrificial structures 150 are removed to create gaps between themandrels 130 and the second masking layer 140. Such sacrificialstructures are referred to as “anti-spacers” in the context of thisdocument. The resulting masking structure may include the mandrels 130and intervening mask features formed of the second masking layer 140(FIG. 2A). Alternatively, the resulting masking structure may includethe mandrels 130 and intervening mask features including the secondmasking layer 140 and the partial gap fillers (FIG. 2B). In someembodiments, the mandrels 130 and the intervening mask featuresalternate with each other, and together define a second pattern.

In some embodiments, the mandrels in the second pattern have a firstpitch between two adjacent mandrels. The intervening mask features inthe second pattern have a pitch substantially the same as the firstpitch. The mandrels and intervening mask features are both used asmasking features for the second pattern. The second pattern has a secondpitch defined by the mandrels and an immediately adjacent one of theintervening mask features. The second pitch is about a half of the firstpitch. Thus, the foregoing process and features provide pitch doubling,that is, the second pattern has a pitch that is half of the pitch of thefirst pattern. In other embodiments, the pitch of the second pattern maybe further reduced by performing an additional process employinganti-spacers as described herein, or by blanket depositing and etchingspacer material to form spacers on sidewalls of the mandrels andintervening mask features.

The methods described herein can be used for forming three dimensionalstructures in a target layer. The three dimensional structures include,but are not limited to, lines, trenches, vias, posts, pillars, troughs,moats, and two or more of the foregoing. In addition, the methods canform structures having different sizes and shapes, for example, variablewidth conductive lines and landing pads.

The methods discussed above and described below in the context ofcertain embodiments allow decreases in pitch and increases in thedensity of features. In addition, the methods allow forming featureshaving various shapes and sizes with a low number of patterning steps.

With reference again to FIGS. 2A and 2B, various processes can beadapted for forming the mandrels 130, the second masking layer 140, thesacrificial structures 150, and/or partial gap fillers 155. Examples ofsuch processes include, but are not limited to, those listed in Table 1.

TABLE 1 Processes Lithography (LG) Furnace (FF) UV cure (UVC) Singlelayer etch (SLE) Chemical vapor UV bake (UVB) deposition (CVD) Multilayer etch (MLE) Physical vapor deposition Vacuum bake (VB) (PVD)Diffusion limited shrink Spin-on deposition (SO) Plating process (PU)(DLS) Diffusion limited growth Wet development (WD) Hard mask (DLG)formation (HM) Thermal freeze (TF) Solvent development Chemical shrink(SD) (CS) Plasma freeze (PF) Dry development (DD) Plasma shrink (PS)Vapor freeze (VF) Plasma etch (PE) Crosslinking (CL) Chemical freeze(CF) Plasma descum (PD) Chemical growth (CG) Exposure freeze (EF)Chemical descum (CD) Plasma growth (PG) Thermal reflow (TR) Slim process(SL) Vapor treatment (VT) Chemical reflow (CR) Image reversal (IR)Silation process (SP) Atomic layer deposition Overcoating (OC) Reactiveion etch (ALD) (RIE) Plasma deposition (PD) Anti-spacer formation Phasechange (PC) (AS) Deprotection process Selectivity change (SEC)Solubility change (DPP) (SC)

The processes and materials of Tables 1 and 2 will be understood bythose of skill in the art, particularly in view of the presentdisclosure. In Table 1, the term “single level etch” refers to a processin which a single layer is provided and etched to form features of apattern. The term “multi level etch” refers to a process in whichmultiple layers are provided and etched to form features of a pattern.The term “diffusion limited shrink” refers to a process in which asolubility change in a feature is caused by a coat, thereby allowing adecrease in a dimension of the feature. The term “diffusion limitedgrowth” refers to a process in which a material is chemically attachedto a pre-existing feature, e.g., through a reaction or adsorption,thereby increasing the dimension of the feature.

The term “freeze” refers to a surface treatment that protects a patternby maintaining the integrity of the boundaries of the features formingthe pattern; for example, freezing a pattern formed by a photoresist toprevent it from dissolving into an overlying photoresist layer. In someinstances, a “freeze” process can be performed to change the chemicalsolubility of a material that is being “frozen.” After the freezeprocess, the frozen material no longer exhibits solubility to solventswhich would otherwise dissolve the material before the freeze process.For example, a photoresist, after being subjected to a freeze process,would be insoluble to solvents, such as propylene glycol monomethylether acetate (PGMEA) or ethyl lactate.

The term “reflow” refers to a process inducing a feature size change, aline increase, and a space decrease, for example, a thermal process thatis designed for such a feature size shift to occur. The term“deprotection process” refers to a process in which a feature protectedfrom a chemical reaction or dissolution by a solvent is released andallowed to become reactive or soluble. The term “furnace” refers to aprocess that includes a thermal bake at a temperature ranging typically,but not limited to, from about 250° C. to about 1000° C. The term“solvent development” refers to a process in which an unconventionalsolvent-based developer (e.g., a solvent other than tetramethylammoniumhydroxide (TMAH)) is used to define a pattern.

The term “descum” refers to a process for removing small portions orresidues of a material. The term “slim process” refers to a process thatinduces a feature size change, namely, a size decrease and a spaceincrease. The term “overcoating” refers to a process of depositing orspinning-on a layer over an existing layer. The term “anti-spacerformation” refers to a process of forming anti-spacers, as describedherein. The term “selectivity change” refers to an etch process havingthe ability to differentiate the etch rate of a target material from theetch rate of a non-target material. The term “plating process” refers toan electrochemical process of depositing a metal on an existinglayer(s). The term “shrink” refers to a process for reducing a size of afeature. The term “plasma growth” refers to a process designed to addadditional material to an existing feature, with assistance of a plasmaoperation. The term “vapor treatment” refers to a process in which a gasphase material is used to interact with a substrate. The term “silationprocess” refers to a process of forming a silane compound. The term“phase change” refers to a process in which a substrate undergoes aphase change during the process. The term “solubility change” refers toa process that changes the solubility of a material in a specificsolution.

The mandrels 130, the second masking layer 140, the sacrificialstructures 150, and/or partial gap fillers 155 may be formed of variousmaterials. Examples of such materials include, but are not limited to,those listed in Table 2.

TABLE 2 Materials oxide (OX) Spin on glass (SOG) nitride (N)Tetraethylorthosilicate (TEOS) silicon oxide (SiO) Metal-containing hardmask (MHM) Silicon hard mask (SHM) Image reversal film (IRF) Titaniumpolymer (TP) tetramethylammonium hydroxide (THAM) developer (TD) Siliconpolymer (SP) Solvent developer (SD) Deposited ARC - SiOxN Gas (GAS)(DARC) Bottom Antireflective Coating Hexamethyldisilazane (HMDS) (BARC)Specific development chemistry Diethylaminotrimethlysilane (DEATS) (SDS)Photoresist (PR) Spin on overcoat (SOO) Deposited underlayer (DUL)Deposited overcoat (DO) Spin on underlayer (SUL) Vapor freeze chemistry(VFC) Reactivity promoter (RP) Solvent suspensions (PGMEA or other)

In Table 2, the term “specific development chemistry” refers to achemical or material, such as butyl acetate or other customized solventsfor development. The term “underlayer” refers to a layer of materialused for a pattern transfer into an underlying layer. The term“reactivity promoter” refers to a chemical agent that promotes thegrowth of an organic material on a feature. A reactivity promoter may ormay not act as a catalyst to a reaction which it promotes. A reactivitypromoter may contribute to the attachment of one material to the surfaceof another material. Thus, it will be appreciated that the variousmaterials of Table 2 may be formed by one or more of the processes ofTable 1. Advantageously, the materials can be combined together andpossibly with other materials to form masks for defining patterns. Thislist is for illustrative purposes only, such that the application of theprocesses noted herein to some embodiments of the invention may beexpressed. The list is not intended to be exhaustive, and as suchmaterials and techniques used in the anti-spacer formation are notlimited to this list.

For example, in certain embodiments, a method is provided for forming amasking pattern for an electronic device, such as an integrated circuit.First, mandrels defining a first pattern are formed in a first maskinglayer deposited over a target layer. As nonlimiting examples, themandrels may be formed of a resist or a hard mask material. A secondmasking layer is deposited on and over the first masking layer to atleast partly bury the first pattern while maintaining the first pattern.The first pattern may be maintained by subjecting the first pattern to asurface treatment using, for example, a so-called freeze technique,prior to depositing the second masking layer.

Portions of the second masking layer proximate to the mandrels arechemically altered such that the portions are more chemically removable(have higher etchability) than unaltered parts of the second maskinglayer. The chemically altered portions are immediately adjacent themandrels and have a selected width, and can be referred to as“anti-spacers” in the context of this document. In some embodiments, thechemical alteration can be achieved by a bake that drives an acid- orbase-initiated reaction using an acid or base diffused from themandrels. The anti-spacers may not expand into the mandrels in thisembodiment.

In some other embodiments, both portions of the mandrels immediatelyadjacent to the second masking layer and portions of the second maskinglayer immediately adjacent to the mandrels may be chemically altered. Insuch embodiments, the altered portions of both the mandrels and thesecond masking layer form anti-spacers. In yet other embodiments,portions of the mandrels immediately adjacent to the second maskinglayer may be chemically altered while substantially no portion of thesecond masking layer is chemically altered, thereby forming anti-spacersonly in the altered portions of the mandrels.

The chemically altered portions are removed, exposing the mandrels. Incertain embodiments, an additional step(s) can be performed to removeany material over the chemically altered portions to expose top surfacesof the chemically altered portions before removing the chemicallyaltered portions. The remainder of the second masking layer formsintervening mask features. The mandrels and the intervening maskfeatures together define a second pattern. The second pattern istransferred into the target layer.

Reference will now be made to the Figures, in which like numerals referto like parts throughout.

FIGS. 3A-3K illustrate a method of forming a masking pattern usinganti-spacers in accordance with some embodiments. Referring to FIG. 3A,a hard mask layer 120 is provided over a target layer 110. In addition,a first resist layer 230 is provided over the hard mask layer 120.

The target layer 110 may be a layer in which various IC components,parts, and structures are to be formed through IC fabrication processes.Examples of the components, parts, and structures include transistors,capacitors, resistors, diodes, conductive lines, electrodes, spacers,trenches, etc. The identity of the target layer material depends on thetype of device to be formed in the target layer 110. Examples of targetlayer materials include, but are not limited to, insulators,semiconductors, and metals. The target layer 110 may be formed over asubstrate, for example, a semiconductor substrate in certainembodiments. In certain other embodiments, at least a portion of asemiconductor substrate forms the target layer 110.

The hard mask layer 120 is a layer that provides a pattern to betransferred into the target layer 110. As described herein, the hardmask layer 120 is patterned to form an array of features that serve as amask for the target layer 110, e.g., in an etch step. While illustratedwith one hard mask layer, the processes described herein can employ twoor more hard mask layers. In certain embodiments, the hard mask layer120 may be omitted.

In some embodiments, the hard mask layer 120 may be formed of aninorganic material. In the illustrated embodiment, the hard mask layer120 is formed of a dielectric anti-reflective coating (DARC), forexample, silicon-rich silicon oxynitride (SiO_(x)N_(y)). The DARC layermay contain silicon in an amount from about 30 wt % to about 80 wt %with reference to the total weight of the layer. The DARC layer maycontain silicon in an amount from 35 wt % to about 70 wt % withreference to the total weight of the layer. In other embodiments, thehard mask layer 120 may be formed of silicon, silicon oxide (SiO₂) orsilicon nitride (Si₃N₄). In yet other embodiments, the hard mask layer120 may be formed of an organic material. For example, the hard masklayer 120 may be formed of amorphous carbon. The skilled artisan willappreciate that various other hard mask materials can be used for thehard mask layer 120. In some embodiments, the hard mask layer 120 mayhave a thickness of between about 80 nm and about 800 nm, optionallybetween about 1 μm and about 3 μm.

The first resist layer 230 may be formed of a first resist material. Thefirst resist material is selected based on the type of lithography usedfor patterning the first resist layer 230. Examples of such lithographyinclude, but are not limited to, ultraviolet (UV) lithography, extremeultraviolet (EUV) lithography, X-ray lithography and imprint contactlithography. In the illustrated embodiment, the first resist material isa photoresist, such as a positive resist. The skilled artisan will,however, appreciate that the material of the first resist layer 230 maybe varied depending on lithography, availability of selective etchchemistries and IC design.

Optionally, a bottom anti-reflective coating (BARC) layer (not shown)may be provided between the first resist layer 230 and the hard masklayer 120. BARCs, which are typically organic, enhance resolution bypreventing reflections of the ultraviolet (UV) radiation that activatesthe photoresist. BARCs are widely available, and are usually selectedbased upon the selection of the resist material and the UV wavelength.BARCs, which are typically polymer-based, are usually removed along withthe overlying photoresist. The optional BARC layer may have a thicknessof between about 200 Å and about 600 Å, optionally between about 300 Åand about 500 Å.

Referring to FIG. 3B, the first resist layer 230 is exposed to a patternof light directed through a photomask over the first resist layer 230.In the illustrated embodiment, the first resist layer 230 is formed of apositive photoresist. Exposed portions 232 of the first resist layer 230become soluble in a developer while unexposed portions 234 of the firstresist layer 230 remain insoluble in the developer. In otherembodiments, the first resist layer 230 may be formed of a negativephotoresist. In such embodiments, exposed portions 234 of the firstresist layer 230 become insoluble in a developer while unexposedportions 232 of the first resist layer 230 remain soluble in thedeveloper.

After the exposure to the pattern of light, the first resist layer 230is subjected to development using any suitable developer. Examples ofdevelopers include, but are not limited to, sodium hydroxide andtetramethylammonium hydroxide (TMAH). In certain embodiments, rinsingsolutions (e.g., propylene glycol monomethyl ether acetate (PGMEA)and/or propylene glycol monomethyl ether (PGME)) can also be used forthe development. In certain embodiments, a post-exposure bake (PEB) maybe performed after the exposure and before the development. In theillustrated embodiment, the exposed portions 232 of the first resistlayer 230 are removed by the development.

Referring to FIG. 3C, the remaining unexposed portions 234 of the firstresist layer 230 form mandrels 234. The mandrels 234 provide a firstpattern 231 while exposing surfaces 122 of the hard mask layer 120. Thefirst pattern 231 has a first pitch P1 between two neighboring mandrels234, as shown in FIG. 3B. Each of the mandrels 234 has a top surface 236and a side surface 238. The illustrated mandrels 234 have asubstantially rectangular or square cross-section. The skilled artisanwill, however, appreciate that the cross-sectional shape of the mandrels234 can be different from that illustrated. For example, thecross-sectional slope can be rounded.

Referring to FIG. 3D, a chemically active species, for example, an acidsolution, is deposited over the structure shown in FIG. 3C. In oneembodiment, the acid solution can be a spin-on coating that covers themandrels 234 and the exposed portions 122 of the hard mask layer 120.The acid solution can include an acid such as a conventional photoresist PAG or other organic acid. Subsequently, a bake process isconducted to thermally diffuse the acid into at least portions of thefeatures 234 that are proximate to the top and side surfaces 236, 238thereof. In some embodiments, the acid may coat the top and sidesurfaces 236, 238 of the features 234 without being diffused into thefeatures 234. In other embodiments where the features 234 are formed ofa material containing a selected amount of acid, this step may beomitted. In certain embodiments, a base solution may be deposited overthe structure in place of the acid solution.

Referring to FIG. 3E, the mandrels 234 may be subjected to a surfacetreatment. The surfaces 236, 238 of the mandrels 234 are modified suchthat the integrity of the mandrels 234 is maintained while a secondresist layer is formed and patterned thereon. The surface treatment mayform a barrier coat or protective layer 236 on the surfaces 236, 238 ofthe mandrels 234. Such a surface treatment can be referred to as“freeze” in the context of this document. The surface treatment may ormay not change the lateral dimensions of the mandrels 234, and may ormay not change the spacings between adjacent mandrels 234.

The mandrels 234 can be frozen by various freeze techniques. In oneembodiment, the mandrels 234 can be frozen by chemical freeze, using acommercially available fluid overcoat. An example of a chemical freezetechnique is disclosed by JSR corporation of Tokyo, Japan in theirpresent product line.

In another embodiment, the mandrels 234 can be frozen by a plasmafreeze. A plasma freeze can be conducted, using a plasma directed to themandrels 234. Examples of plasmas include a fluorine-containing plasmagenerated from, e.g., a fluorocarbon (e.g., CF₄, C₄F₆, and/or C₄F₈), ahydrofluorocarbon (e.g., CH₂F₂, and/or CHF₃), or NF₃. An example plasmafreeze technique is disclosed by U.S. patent application Ser. No.12/201,744, filed Aug. 29, 2008, entitled “METHODS OF FORMING APHOTORESIST-COMPRISING PATTEN ON A SUBSTRATE” (Inventors: Zhang et al.).In yet another embodiment, the mandrels 234 can be frozen by a thermalfreeze. The thermal freeze can be conducted at a temperature betweenabout 110° C. and about 180° C. An example of a thermal freeze techniqueis disclosed by Tokyo Ohka Kogyo Co., Ltd. of Kawasaki-shi, KanagawaPrefecture, Japan in their commercially available products.

Referring to FIG. 3F, a second resist layer 240 is blanket depositedover the mandrels 234 and the exposed surfaces 122 of the hard masklayer 120. The second resist layer 240 can have a substantially planartop surface 244. The second resist layer 240 may be formed of a secondresist material. The second resist material may be of the samecomposition as the first resist material or of a different compositionfrom the first resist material. The first and second resist materialsmay be of the same or different type with regard to being positive ornegative photoresist.

In some embodiments, the second resist material may include a chemicallyamplified photoresist. The chemically amplified photoresist may be anacid-catalyzed or base-catalyzed material. Examples of chemicallyamplified photoresists include, but are not limited to, 193 nm and 248nm photo resists. Some Mine materials are also chemically amplified.

In certain embodiments, the second resist material may include a bottomanti-reflective coating (BARC) material modified to be suitable for asolubility change by acid or base diffusion. The skilled artisan willappreciate that any material showing a solubility change caused by theacid or base diffusion can be used in place of the second resistmaterial.

The second resist layer 240 may be formed to have a thickness sufficientto cover the top surface 236 of the mandrels 234. Portions 242 of thesecond resist layer 240 overlying the top surfaces 236 of the mandrels234 can be referred to as “top coat” in the context of this document.The top coats 242 may have a thickness selected such that all theresulting masking features have substantially the same height after thefrozen mandrels 234 and other features that will be formed from portionsof the second resist layer 240 are subjected to development. Theresulting masking features will form a pattern to be transferred intothe underlying target layer 110.

Referring to FIG. 3G, the structure of FIG. 3F is subjected to a bake.In one embodiment, the bake may be conducted at a temperature of about110° C. to about 220° C. for about 0.5 min. to about 3 min. In anotherembodiment, the bake may be conducted at a temperature of about 110° C.to about 160° C. In embodiments where the second resist layer 240 isformed of an acid-catalyzed chemically amplified resist, the bake drivesan acid-catalyzed reaction that alters the solubility of the secondresist layer 240 in a developer. The acid-catalyzed reaction changesportions 250 of the second resist layer 240 that are proximate to themandrels 234, causing those changed portions to become soluble in thedeveloper. The portions 250 of the second resist layer 240 may includethe top coats 242 of the second resist layer 240 and portions 244adjoining the side surfaces 238 of the mandrels 234. The portions 250that become soluble can be referred to as “anti-spacers.”

The acid-catalyzed reaction is initiated at or near the top and sidesurfaces 236, 238 of the mandrels 234 during the bake step. For example,an acid diffused into the mandrels 234 during the step of FIG. 3D nowdiffuses into the top coats 242 and the adjoining portions 244 of thesecond resist layer 240 (as indicated by arrows in FIG. 3G), and changesthe solubility of the portions 242, 244, thereby forming anti-spacers250 around and on top of the mandrels 234. The width W1 of theanti-spacers 250 can be controlled by changing, for example, the baketime and/or temperature, the porosity of layer 240, and the size of acidspecies.

In other embodiments where the second resist layer 240 is formed of abase-catalyzed chemically amplified resist, the bake drives abase-catalyzed reaction that may alter the solubility of the secondresist layer 240 in a developer. In such an embodiment, a base solutionis provided in the step of FIG. 3D, rather than an acid solution. Theskilled artisan will appreciate that anti-spacers can be formed in thesame manner as in the embodiment described herein in connection withFIG. 3G.

In certain embodiments, other portions (not shown) of the second resistlayer 240 may be optionally exposed to a pattern of light before orafter the bake step. This exposure step can be used to form patterns inthe other areas by photolithography, rather than by forminganti-spacers. During this optional exposure step, the structure shown inFIG. 3F or 3G may be blocked from light, if the structures are formed ofa positive photoresist. This optional exposure step can form structureslarger in width than the structures shown in FIG. 3H. In certainembodiments, the optional exposure step can be used to form structuresin a peripheral region of an IC device or substrate while methodsemploying anti-spacers can be used to form structures in an array regionof the IC device or substrate.

Referring to FIG. 3H, the structure resulting from the step of FIG. 3Gis subjected to development which serves to selectively remove theanti-spacers 250. Any suitable developer may be used to remove theanti-spacers 250 (FIG. 3G). Examples of developers include, but are notlimited to, sodium hydroxide and tetramethylammonium hydroxide (TMAH).In certain embodiments, rinsing solutions (e.g., propylene glycolmonomethyl ether acetate (PGMEA) and/or propylene glycol monomethylether (PGME)) can also be used for the development. In one embodiment,this development step can be performed at room temperature for about 0.5min. to about 3 min.

This step exposes the pre-existing mandrels 234 while definingintervening mask features 248 formed of the second resist material. Theillustrated intervening mask features 248 have a T-shaped top portion,but the skilled artisan will appreciate that the shape of theintervening mask features 248 can vary, depending on the conditions(e.g., temperature, duration, etc.) of the development. The mandrels 234may have a first height H1 and the intervening mask features 248 mayhave a second height H2 that is greater than the first height H1.

Referring to FIG. 3I, the developer may also anisotropically remove atleast part of top portions of the mandrels 234 and the intervening maskfeatures 248. The mandrels 234, which have been frozen, may be developedat a slower rate than the intervening mask features 248. Thus, after thecompletion of the development, the mandrels 234 and the intervening maskfeatures 248 can have substantially the same height H3 as each other ifthe thicknesses of the top coats 242 of the second layer 240 have beenselected such that the heights of the mandrels 234 and the interveningmask features 248 are substantially the same as each other after thedevelopment. As shown in FIG. 3I, both of the mandrels 234 and theintervening mask features 248 can have rounded top portions. In certainembodiments, an isotropic etch process may be conducted after thedevelopment to reduce the widths of the mandrels 234 and the interveningmask features 248.

The mandrels 234 and the intervening mask features 248 together providea second pattern 260, as shown in FIG. 3I. The second pattern 260 has asecond pitch P2 between neighboring features. The second pitch P2 isabout half of the first pitch P1 in the illustrated embodiment.

Referring to FIG. 3J, an etch step is conducted to transfer the secondpattern 260 into the underlying hard mask layer 120. The second pattern260 may be transferred into the hard mask layer 120 using any suitableetch process. The etch process can be a dry or wet etch process. In oneembodiment, the etch process can be a plasma etch process, for example,a high density plasma etch process. The plasma etch process may be ananisotropic etch process.

Referring to FIG. 3K, the target layer 110 is etched through the hardmask layer 120. As a result, trenches or troughs 205 are formed in thetarget layer 110. In some embodiments, through-holes can be formedthrough the target layer 110.

In certain embodiments, an etch stop layer (not pictured) can be usedbetween the hard mask layer 120 and the target layer 110. The etch stopcan be made of, for example, DARC or silicon nitride, depending upon thecomposition of the target layer 110. The etch stop avoids damage to thetarget layer 110 during the etching of the hard mask layer 120, such asduring pattern transfer to the hard mask layer 120 or during removal ofthe hard mask layer 120. This may be particularly desirable when thetarget layer 110 is a metal, such as a metallization layer.

When processing (e.g., etching) of the target layer is completed, thehard mask layer 120 and the overlying features 234, 248 may be removedby etch processes, such as a wet etch. Subsequently, additional stepssuch as metallizations may be conducted to form integrated circuits.

FIGS. 4A-4H illustrate a method of forming a masking pattern usinganti-spacers in accordance with other embodiments. In these embodiments,the mandrels are formed from a hard mask layer or other material otherthan a photoresist layer. Referring to FIG. 4A, the method includesproviding the target layer 110. Details of the target layer 110 can beas described above in connection with FIG. 3A.

A hard mask layer is formed over the target layer 110. In someembodiments, the hard mask layer may be formed of a silicon-containingorganic material. The silicon-containing organic layer may containsilicon in an amount from about 10 wt % to about 35 wt % with referenceto the total weight of the layer. An example of a silicon-containingorganic materials includes, but is not limited to, SHB-A629 (availablefrom Shin Etsu, Tokyo, Japan). In such an embodiment, the hard masklayer may have a thickness of between about 40 nm and about 800 nm,optionally between about 1 μm and about 3 μm.

The hard mask layer is then patterned to form mandrels 330, as shown inFIG. 4A. The hard mask layer can be patterned using any suitableprocess, including, but not limited to, a photolithographic process inwhich photoresist is patterned and the pattern is transferred to thehard mask layer. The mandrels 330 are spaced apart from one another andhave a first pitch P1 and expose surfaces 112 of the target layer 110.

Referring to FIG. 4B, a chemically active species, for example, an acidsolution, is deposited on the structure shown in FIG. 4A. In oneembodiment, the acid solution can be spin-on deposited on the structureto cover the mandrels 330 and the exposed surfaces 112 of the targetlayer 110. The acid solution can include any organic acid, such as aPAG. Subsequently, a bake process is conducted to thermally diffuse theacid into at least portions of the mandrels 330 proximate to the top andside surfaces 332, 334 of the mandrels 330. In this embodiment, themandrels 330 are at least partially permeable to the acid while thetarget layer 110 is substantially impermeable to the acid. Thus, themandrels 330 can have an acid coat 326 on the surfaces 332, 334 thereofwhile the exposed portions 112 of the target layer 110 do not have anacid coat formed thereon, as shown in FIG. 4C. In other embodiments, thechemically active species may be in the form of a gas or may be in thesolid state.

Referring to FIG. 4D, a resist layer 340 is formed over the mandrels 330and the exposed portions 112 of the target layer 110 and may have asubstantially planar top surface 344. The resist layer 340 may be formedof a resist material that is the same as the second resist materialdescribed above in connection with FIG. 3F. In one embodiment, theresist material may include a chemically amplified resist. Thechemically amplified resist may be either acid-catalyzed orbase-catalyzed. In other embodiments where the resist material is abase-catalyzed resist, a base coat (rather than an acid coat) isprovided over the mandrels 330 and the exposed portions 112 of thetarget layer 110 in the step of FIG. 4C. Other details of forming theresist layer 340 can be as described above in connection with FIG. 3F.

Referring to FIG. 4E, the structure resulting from the step of FIG. 4Dis subjected to a bake. The bake forms anti-spacers 350 at the sides andon top of the mandrels 330. Other details of the bake step can be asdescribed in connection with FIG. 3G.

In certain embodiments, other portions (not shown) of the resist layer340 may be optionally exposed to a pattern of light before or after thebake step of FIG. 4E. This exposure step can be used to form patterns inthe other portions by photolithography, rather than by forminganti-spacers. During this optional exposure step, the structure shown inFIG. 4E may be blocked from light, if the structures are formed of apositive photoresist. This optional exposure step can form structureslarger in width than the structures shown in FIG. 4F. In certainembodiments, the optional exposure step can be used form structures in aperipheral region of an IC device or substrate while methods employinganti-spacers can be used to form structures in an array region of the ICdevice or substrate.

Referring to FIG. 4F, the structure resulting from the step of FIG. 4Eis subjected to development to remove the anti-spacers 350. This stepexposes the pre-existing mandrels 330 formed of the hard mask materialwhile forming intervening mask features 345 formed of the resistmaterial. The illustrated intervening mask features 345 have a T-shapedtop portion, but the skilled artisan will appreciate that the shape ofthe intervening mask features 345 can vary, depending on the conditions(e.g., temperature, duration, etc.) of the development. The mandrels 330may have a first height H1 and the intervening mask features 345 have asecond height H2 that is greater than the first height H1.

The developer can also remove at least part of the top portions of theintervening mask features 345. However, the mandrels 330, which areformed of a hard mask material, may not be eroded by the developer.Thus, after the completion of the development, the mandrels 330 and theintervening mask features 345 may have substantially the same height H3as each other. As shown in FIG. 4G, the mandrels 330 may retain theiroriginal shape while the intervening mask features 345 may have roundedtop portions.

The mandrels 330 and the intervening mask features 345 together providea second pattern 360, as shown in FIG. 4G. The second pattern 360 has asecond pitch P2 between a mandrel 330 and a neighboring intervening maskfeature 345. The second pitch P2 is about half of the first pitch P1 inthe illustrated embodiment.

Referring to FIG. 4H, an etch step is conducted to transfer the secondpattern 360 into the target layer 110. The second pattern 360 may betransferred into the target layer 110 using any suitable etch process.The etch process can be a dry or wet etch process. In one embodiment,the etch process can be a plasma etch process, optionally a high densityplasma etch process. The plasma etch process may be an anisotropic etchprocess. Other details of this step can be as described above inconnection with FIG. 3K.

In the illustrated embodiment, trenches or troughs 305 (or through-holesin other embodiments) are formed in the target layer 110. Because themandrels 330 (formed of a hard mask material) may be etched at a fasterrate than the intervening mask features 345 (formed of a photoresist)during the transfer step of FIG. 4H, the height H4 of the remainingmandrels 330 may be greater than the height H5 of the remainingintervening mask features 345 after the completion of the transfer step.

When processing (e.g., etching) of the target layer 110 is completed,the mandrels 330 and the intervening mask features 345 may be removed byknown etch processes, such as a wet etch step. Subsequently, additionalsteps such as metallization may be conducted to complete integratedcircuits.

FIGS. 5A-5D illustrate a method of forming a masking pattern usinganti-spacers in accordance with yet other embodiments. Referring to FIG.5A, the method includes providing the target layer 110. Details of thetarget layer 110 can be as described above in connection with FIG. 3A.Hard mask layer 120 is formed on the target layer 110. Details of thehard mask layer 120 can be as described above in connection with FIG.3A. In certain embodiments, the hard mask layer 120 may be omitted.

Then, mandrels 430 are formed of a photoresist material on the hard masklayer 120. Details of forming the mandrels 430 can be as described abovein connection with FIGS. 3A-3C. The mandrels 430 provide a first pattern431 while exposing surfaces 122 of the hard mask layer 120. The firstpattern 431 has a first pitch P1 between two neighboring mandrels 430,as shown in FIG. 5A. Each of the mandrels 430 has a top surface 436 anda side surface 438. The illustrated mandrels 430 have a substantiallyrectangular or square cross-section. The skilled artisan will, however,appreciate that the cross-sectional shape of the mandrels 430 can bedifferent from that illustrated.

Then, a chemically active species 432, for example, an acid or basesolution, is deposited on the structure shown in FIG. 5A. In someembodiments, the acid or base solution can be spin-on deposited on thestructure to cover the mandrels 430 and the exposed portions 122 of thehard mask layer 120. The details of the acid or base solution can be asdescribed above in connection with FIG. 3D.

Referring to FIG. 5B, the structure of FIG. 5A is subjected to a bake.The details of the bake can be as described above in connection withFIG. 3G. The bake drives an acid- or base-catalyzed reaction that altersthe solubility of portions 452, 454 of the mandrels 430. The acid- orbase-catalyzed reaction changes top portions 452 and side portions 454of the mandrels 430, causing those changed portions to become soluble ina developer. The top and side portions 452, 454 of the mandrels 430 formanti-spacers 450. Thus, the resulting mandrels 430′ have a reduced sizeboth vertically and horizontally. Such mandrels 430′ can be referred toas reduced mandrels in the context of this document.

Subsequently, the reduced mandrels 430′ covered with the anti-spacers450 may be subjected to a surface treatment. Surfaces of theanti-spacers 450 are modified such that the integrity of the mandrels ismaintained while a second resist layer is formed thereon. The details ofthe surface treatment can be as described above in connection with FIG.3E.

Referring to FIG. 5C, a second masking layer 440 is blanket depositedover the anti-spacers 450 and the exposed surfaces 122 of the hard masklayer 120. In other embodiments, the second masking layer may have asmaller height than the anti-spacers such that the second masking layersurrounds sidewalls of the anti-spacers while exposing top surfaces ofthe anti-spacers. The second masking layer 440 may be formed of an imagereversal material, such as an Image Reversal Overcoat (IROC) materialand other similar materials, e.g., as outlined in US Patent ApplicationPublication No. 2009/0081595 from Shin-Etsu Chemical Co., Ltd (Tokyo,Japan). Bottom Anti-Reflection Coating (BARC) materials can also be usedfor the second masking layer 440. Other details of this step can be asdescribed above in connection with FIG. 3F.

In the illustrated embodiment, the second masking layer 440 may beformed to have a thickness sufficient to cover the top portions 452 ofthe anti-spacers 450. Portions of the second masking layer 440 overlyingthe top portions 452 of the anti-spacers 450 may be referred to as “topcoats” in the context of this document.

Referring to FIG. 5D, the structure resulting from the step of FIG. 5Cis subjected to development. Any suitable developer may be used toremove the anti-spacers 450 (FIG. 5C). This step exposes the reducedmandrels 430′ while defining intervening mask features 448 formed of thematerial of the second masking layer 440.

The reduced mandrels 430′ and the intervening mask features 448 togetherprovide a second pattern 460. The second pattern 460 has a second pitchP2 between a reduced mandrel 430′ and a neighboring intervening maskfeature 448. The second pitch P2 is about half of the first pitch P1(FIG. 5A) in the illustrated embodiment. Other details of this step canbe as described above in connection with FIG. 3H. The step shown in FIG.5D can be followed by steps as described above in connection with FIGS.3I to 3K to transfer the second pattern 460 into the target layer 110.

In some other embodiments, mandrels defining a first pattern are formedin a first masking layer provided over a target layer. One or moresacrificial structures may be formed by conformally growing ordepositing a layer to cover at least exposed sidewall surfaces of themandrels. The layer may be formed of a material that is different fromthat of the first masking layer.

A second masking layer is deposited to fill spaces defined by themandrels covered with the sacrificial structures. In some embodiments,the second masking layer may cover top surfaces and sidewalls of themandrels covered with the sacrificial structures. In such embodiments,an additional step(s), e.g., a descum step, can be performed to removeportions of the second masking layer over the sacrificial structures toexpose top surfaces of the sacrificial structures. In other embodiments,the second masking layer may have a smaller height than the anti-spacerssuch that the second masking layer surrounds sidewalls of theanti-spacers while exposing top surfaces of the anti-spacers. The secondmasking layer may be formed of a material different from the material ofthe sacrificial structures.

Then, the sacrificial structures are removed, exposing the mandrels. Theremaining parts of the second masking layer form intervening maskingfeatures. The mandrels and the intervening mask features together definea second pattern. The second pattern is transferred into the targetlayer.

FIGS. 6A-6E illustrate a method of forming a masking pattern by growinganti-spacers. In these embodiments, mandrels may be formed from a hardmask layer or other material other than a photoresist layer, asdiscussed with reference to FIG. 4A.

Referring to FIG. 6A, the target layer 110 is provided. Details of thetarget layer 110 can be as described above in connection with FIG. 3A. Ahard mask layer is formed over the target layer 110, and is patterned toform mandrels 330, as shown in FIG. 6A. The mandrels 330 are spacedapart from one another with a first pitch P1 while exposing surfaces 112of the target layer 110. Each of the mandrels 330 has a top surface 332and side surfaces 334. Other details of this step can be as describedabove in connection with FIG. 4A.

Referring to FIG. 6B, a sacrificial material, such as an organicmaterial, is grown on the top and side surfaces 332, 334 of the mandrels330, while exposing substantial portions of the exposed surfaces 112 ofthe target layer 110. Examples of such organic materials include, butare not limited to, perhydropolysilazane (PHPS) or polyhedral oligomericsilsesquioxanes (POSS). The organic material can be grown by a diffusionlimited growth technique. In some embodiments, the reaction temperaturemay be between about 100° C. and about 180° C., which may be below theglass transition temperature Tg of the original mandrel material.Attachment of the sacrificial material may be catalyzed by another wettreatment or a material that may be present in the chemical formulationof the mandrel. Critical dimensions can then be modulated by controllingreaction temperature in combination with the chemical compositions usedin the sacrificial material. The organic material forms anti-spacers 650that include top portions 652 and side portions 654 covering the top andside surfaces 332, 334, respectively, of the mandrels 330.

Referring to FIG. 6C, a second masking layer 640 is blanket depositedby, for example, spin-on deposition, over the anti-spacers 650 and theexposed surfaces 112 of the target layer 110. The second masking layer440 may be formed of a silicon hard mask material, such as STH1125Bmanufactured by Shin-Etsu Chemical Co., Ltd (Tokyo, Japan) or similarcommercial hardmask material readily available to those versed in theart. Other details of this step can be as described above in connectionwith FIG. 5C. In the illustrated embodiment, the second masking layer640 may be formed to have a thickness sufficient to slightly cover topportions 652 of the anti-spacers 650. Portions of the second maskinglayer 640 overlying the top portions 652 of the anti-spacers 650 may bereferred to as “top coats” in the context of this document.

Referring to FIG. 6D, the structure resulting from the step of FIG. 6Cis subjected to a chemical descum process. The chemical descum processserves to remove the top coats of the second masking layer 640, therebyexposing the top portions 652 of the anti-spacers 650. As non-limitingexamples, the chemical descum may be performed using a wet etch or aplasma etch such as a buffered oxide etch (BOE) dip process or Argonsputter etch. Tetramethylammonium hydroxide (TMAH) developer can also beused to clean up these feature areas at a temperature ranging from about10° C. to about 50° C.

Referring to FIG. 6E, the structure resulting from the step of FIG. 6Dis subjected to an etch process to remove the anti-spacers 650. Anysuitable etchant may be used to remove the anti-spacers 650, dependingon the organic material. In some embodiments where the organic materialis a pure hydrocarbon-based material, the etchant can be a dry etchant,such as O₂ or halide-based plasma, or a wet etchant, such astetramethylammonium hydroxide (TMAH), propylene glycol monomethyl ether(PGME), propylene glycol monomethyl ether acetate (PGMEA), or any othersuitable organic solvent. This step exposes the mandrels 330 formed ofthe hard mask material while defining intervening mask features 645formed of the silicon hard mask material or mandrel material that mayhave used a process to ensure that its solubility is compatible with thewet etch. For the purpose of this document, such processes can be“freeze” techniques and they serve to limit the solubility of themandrels in a wet etch process. These “freeze” techniques can take onvarious forms, for example, a thermal cross linking agent in a resist.

The mandrels 330 and the intervening mask features 645 together define asecond pattern 660. The second pattern 660 has a second pitch P2 betweena mandrel 330 and a neighboring intervening mask feature 645. The secondpitch P2 is about half of the first pitch P1 in the illustratedembodiment. Other details of this step can be as described above inconnection with FIG. 3H. The step shown in FIG. 6E can be followed bysteps as described above in connection with FIGS. 3I to 3K to transferthe second pattern 660 into the target layer 110.

FIGS. 7A-7F illustrate a method of forming a masking pattern usinganti-spacers in accordance with yet other embodiments. In theseembodiments, mandrels may be formed from a hard mask layer or any othersuitable material, using a process that allows selective growth ofanti-spacers. A photoresist can be used in the step shown in FIG. 7A aslong as it is appropriately mated to the processing requirements, e.g.,with regard to solubility. In such an embodiment, a photoresist usedherein can withstand subsequent process steps. This can be achieved witha different solvent resist system, such as an alcohol-based resist orcan be achieved with a “freeze” technique.

Referring to FIG. 7A, the method includes providing the target layer110. Details of the target layer 110 can be as described above inconnection with FIG. 3A. A hard mask layer is formed over the targetlayer 110, and is patterned to form mandrels 330, as shown in FIG. 7A.The mandrels 330 are spaced apart from one another with a first pitch P1while exposing surfaces 112 of the target layer 110. Each of themandrels 330 has a top surface 332 and side surfaces 334. Other detailsof this step can be as described above in connection with FIG. 4A.

Referring to FIG. 7B, a reactivity promoter 655 is deposited on the topand side surfaces 332, 334 of the mandrels 330 without covering theexposed surfaces 112 of the target layer 110. The reactivity promoterserves to facilitate the growth of an organic material on the surfacesof the mandrels 330 at the next step. Examples of such reactivitypromoters include, but are not limited to, AZ materials used in RELACS(Resolution Enhancement Lithography Assisted by Chemical Shrink)processes, and a material including a hydroxyl group or organic aciddesigned to condition the reactivity of the mandrels to a material thatcovers the mandrels.

Referring to FIG. 7C, a sacrificial material, such as an organicmaterial, is grown on the top and side surfaces 332, 334 of the mandrels330 that are covered with the reactivity promoter 655. The organicmaterial does not cover the exposed surfaces 112 of the target layer 110except for portions 112 a of the exposed surfaces 112 proximate to themandrels 330. Examples of such organic materials include, but are notlimited to, PHPS or a chain hydrocarbon with a bonding affinity to themandrels covered with the reactivity promoter. The organic material canbe grown by a diffusion limited growth technique by means of a fluidovercoat at a controlled temperature, for example, in a range betweenabout 10° C. and about 180° C. The organic material forms anti-spacers650 that cover the top and side surfaces 332, 334 of the mandrels 330.

Referring to FIG. 7D, a second masking layer 640 is blanket depositedby, for example, spin-on deposition, over the anti-spacers 650 and theexposed surfaces 112 of the target layer 110. The second masking layer640 can optionally cover top surfaces of the anti-spacers 650. Thesecond masking layer 640 may be formed of, for example, a silicon hardmask material. The details of this step can be as described above inconnection with FIG. 6C.

Referring to FIG. 7E, the structure resulting from the step of FIG. 7Dis subjected to a chemical descum process. The details of this step canbe as described above in connection with FIG. 6D.

Referring to FIG. 7F, the structure resulting from the step of FIG. 7Eis subjected to an etch process to remove the anti-spacers 650. Thedetails of this step can be as described above in connection with FIG.6E. This step exposes the mandrels 330 formed of the hard mask materialwhile defining intervening mask features 645 formed of the materialforming the second masking layer 640, e.g., a silicon hard maskmaterial.

The mandrels 330 and the intervening mask features 645 together define asecond pattern 660. The second pattern 660 has a second pitch P2 betweena mandrel 330 and a neighboring intervening mask feature 645. The secondpitch P2 is about half of the first pitch P1 in the illustratedembodiment. Other details of this step can be as described above inconnection with FIG. 3H. The step shown in FIG. 7F can be followed bysteps as described above in connection with FIGS. 3I to 3K to transferthe second pattern 660 into the target layer 110.

FIGS. 8A-8F illustrate a method of forming a masking pattern usinganti-spacers in accordance with yet other embodiments. In theseembodiments, mandrels may be formed from a hard mask layer or any othersuitable material compatible with blanket deposition of an anti-spacermaterial, including materials discussed with reference to FIG. 4A.

Referring to FIG. 8A, the method includes providing a target layer 110.Details of the target layer 110 can be as described above in connectionwith FIG. 3A. A hard mask layer is formed over the target layer 110, andis patterned to form mandrels 330, as shown in FIG. 8A. The mandrels 330are spaced apart from one another with a first pitch P1 while exposingsurfaces 112 of the target layer 110. Each of the mandrels 330 has a topsurface 332 and side surfaces 334. Other details of this step can be asdescribed above in connection with FIG. 4A.

Referring to FIG. 8B, a sacrificial material is conformally deposited onthe top and side surfaces 332, 334 of the mandrels 330 and the exposedsurfaces 112 of the target layer 110. Examples of such sacrificialmaterials include, but are not limited to, BARC, DARC, photoresist,silicon-on-glass (SOG), and hardmask type material. The sacrificialmaterial can be deposited by, for example, spin-on coat or deposition.Portions 852, 854 of the sacrificial material that cover the top andside surfaces 332, 334, respectively, of the mandrels 330 formanti-spacers 850. Portions 855 of the sacrificial material formed on thesurfaces 112 of the target layer 110 may be referred to as “partial gapfillers” in the context of this document.

Referring to FIG. 8C, a second masking layer 640 is deposited over thepartial gap fillers 855 and can also extend over the anti-spacers 850.Other details of this step can be as described above in connection withFIG. 6C.

Referring to FIG. 8D, to expose anti-spacers 850 in embodiments wherethe anti-spacers 850 are covered, the structure resulting from the stepof FIG. 8C is subjected to a chemical descum process. The details ofthis step can be as described above in connection with FIG. 6D.

Referring to FIG. 8E, the structure resulting from the step of FIG. 8Dis subjected to an etch process to remove the anti-spacers 850. The etchprocess may use an anisotropic etch process, using any suitable dryetchant, such as C₂F₄, O₂, Hbr, or F₂. In one embodiment where theorganic material is a photoresist, the etchant can be a dry etchant,such as C₂F₄, O₂, Hbr, and F₂. This step exposes the mandrels 330 formedof the hard mask material while defining intervening mask features 845between the mandrels 330. Each of the features 845 includes a structure645 formed of the silicon hard mask material and a partial gap filler855 underlying the structure 645.

The mandrels 330 and the intervening mask features 845 together define asecond pattern 860. The second pattern 860 has a second pitch P2 betweena mandrel 330 and a neighboring intervening mask feature 845. The secondpitch P2 is about half of the first pitch P1 in the illustratedembodiment. Other details of this step can be as described above inconnection with FIG. 3H. The step shown in FIG. 8E can be followed bysteps as described above in connection with FIGS. 3I to 3K to transferthe second pattern 860 into the target layer 110.

In some embodiments, a masking pattern formed by the methods describedherein may be used for further pitch multiplication. The pitch of themasking pattern may be further reduced by conducting an additionalprocess using anti-spacers. For example, anti-spacers may be formedaround the mask features left after anti-spacer removal, e.g., includingthe mandrels 234 and intervening mask features 248, as shown in FIG. 3I,and the pitch of the resulting features can be reduced to about half ofthe second pitch P2.

In such embodiments, a second set of anti-spacers are formed around andoptionally over the mask features by repeating the steps of FIGS. 3D-3I,FIGS. 4A-4E, FIGS. 5A-5C, FIGS. 6A-6D, FIGS. 7A-7E, or FIGS. 8A-8D. Insome embodiments, the second set of anti-spacers may be formed bydepositing a third masking layer to at least partially bury the secondpattern and chemically altering portions of the third masking layer toform the second set of anti-spacers, as in the steps shown in FIGS.3D-3I, FIGS. 4A-4E, or FIGS. 5A-5C. In other embodiments, the second setof anti-spacers may be formed by growing a second set of anti-spacers onthe mask features, as in the steps shown in FIGS. 6A-6D, FIGS. 7A-7E, orFIGS. 8A-8D, and a third masking layer is deposited to fill spacesbetween the mask features covered with the anti-spacers.

Subsequently, the second set of anti-spacers are removed while leavingat least portions of the third masking layer to form additionalintervening mask features. The mandrels, the intervening mask features,and the additional intervening mask features together define a thirdpattern having a pitch that is about a half of the pitch of the secondpattern. The skilled artisan will appreciate that further pitchmultiplication is also possible by repeating the process of forming andremoving anti-spacers. The steps described above can be repeated ifdesired for more pitch reduction.

In other embodiments, a masking pattern formed by the methods describedabove may be used for additional pitch multiplication in combinationwith a process employing so-called spacers.

FIGS. 9A-9D illustrate a method of forming a masking pattern, usinganti-spacers and spacers in accordance with one embodiment. In theillustrated embodiment, features forming a masking pattern can have asmaller pitch than the pitches P2 of the second patterns 260, 360, 460,660, and 860 described above in connection with FIGS. 3I, 4G, 5D, 6E,7F, and 8E.

Referring to FIG. 9A, the target layer 110 is provided. The details ofthe target layer 110 can be as described above in connection with FIGS.3A, 4A, 5A, 6A, 7A, and 8A.

A first pattern 920 is formed on the target layer 110. The first pattern920 may include mandrels 922 and intervening mask features 924. In thecontext of this embodiment, the mandrels 922 and the intervening maskfeatures 924 may be collectively referred to as “first maskingfeatures.” The mandrels 922 and the intervening mask features 924 can beformed by the method described above in connection with FIGS. 3A-3I,FIGS. 4A-4G, FIGS. 5A-5D, FIGS. 6A-6E, FIGS. 7A-7F, or FIGS. 8A-8E. Incertain embodiments, one or more hard mask layers (not shown) can beformed on the target layer 110, and the first pattern 920 can be formedon the one or more hard mask layers. The first pattern 920 maycorrespond to any one of the second patterns 260, 360, 460, 660, and 860described above in connection with FIGS. 3I, 4G, 5D, 6E, 7F, and 8E.

As shown in FIG. 9A, the mandrels 922 have a first pitch P1therebetween. In the first pattern 920, however, two neighboring firstmasking features (i.e., a mandrel 922 and a neighboring intervening maskfeature 924) have a second pitch P2 that is about half of the firstpitch P1. In some embodiments, the first masking features 922, 924 inthe first pattern 920 may be trimmed or shrunk by an isotropic etchingprocess to increase the distance between neighboring features.

Next, as shown in FIG. 9B, a layer 930 of spacer material may beblanket-deposited conformally over exposed surfaces, including thetarget layer 110 and the tops and sidewalls of the first maskingfeatures 922, 924.

The spacer material can be any material capable of use as a mask totransfer a pattern to the underlying target layer 110. The spacermaterial preferably: 1) can be deposited with good step coverage, 2) canbe deposited at a temperature compatible with the target layer 110 and3) can be selectively etched relative to the target layer 110. In oneembodiment, the spacer material 930 is silicon oxide. In othernon-limiting embodiments, the spacer material may be polysilicon or alow temperature oxide (LTO).

The spacer material may be deposited by any suitable method, including,but not limited to, chemical vapor deposition (CVD), atomic layerdeposition (ALD), spin-coating, or casting. ALD may have the advantagesof both low temperature deposition and high conformality. The thicknessof the layer 930 corresponds to the width of the spacers 935 and may bedetermined based upon the desired width of those spacers 935 (FIG. 9C).For example, in some embodiments, the layer 930 may be deposited to athickness of about 20-80 nm and, optionally, about 40-60 nm. In someembodiments, the step coverage is about 80% or greater and, optionally,about 90% or greater.

In certain embodiments, the spacer material may be one of a class ofmaterials available from Clariant International, Ltd. (so-called “AZ R”materials), such as the materials designated as AZ R200™, AZ R500™, andAZ R600™. In other embodiments, the spacer material may be an “AZ R”material with one or more inorganic components (e.g., one or more oftitanium, carbon, fluorine, bromine, silicon, and germanium) dispersedtherein. The “AZ R” materials contain organic compositions whichcross-link upon exposure to acid released from chemically-amplifiedresist. Specifically, an “AZ R” material may be coated acrossphotoresist, and subsequently the resist may be baked at a temperatureof about 100° C. to about 120° C. to diffuse acid from the resist andinto the “AZ R” material to form chemical cross-links within regions ofthe material proximate the resist. Portions of the material adjacent theresist are thus selectively hardened relative to other portions ofmaterial in which acids have not diffused. The material may then beexposed to conditions which selectively remove the non-hardened portionsrelative to the hardened portions. Such removal may be accomplishedusing, for example, 10% isopropyl alcohol in the ionized water, or asolution marketed as “SOLUTION C™” by Clariant International, Ltd. Theprocesses using the “AZ R” materials are sometimes considered examplesof RELACS (Resolution Enhancement Lithography Assisted by ChemicalShrink) processes. Examples of spacers formed by RELACS processes aredisclosed by U.S. patent application Ser. No. 12/125,725, filed May 22,2008, entitled “METHODS OF FORMING STRUCTURES SUPPORTED BY SEMICONDUCTORSUBSTRATES” (inventor: Anton deVilliers).

Referring to FIG. 9C, the spacer layer 930 is then subjected to ananisotropic etch to remove spacer material from horizontal surfaces 912of the target layer 110 and the first masking features 922, 924. In anembodiment where the spacer layer 930 is formed of a silicon oxidematerial, an etch, also known as a spacer etch, can be performed on thesilicon oxide material, using a fluorocarbon plasma, e.g., containingCF₄/CHF₃, C₄F₈/CH₂F₂ or CHF₃/Ar plasma. The etchants are chosen to beselective for the spacer material relative to the target layer 110.

Referring to FIG. 9D, the first masking features 922, 924 are removed toleave freestanding spacers 935. In one embodiment, the first maskingfeatures 922, 924 may be removed by an oxygen-containing plasma etch,such as an etch using HBr/O₂/N₂ and SO₂/O₂.

In the illustrated embodiment, the spacers 935 form a second pattern 950having a third pitch P3. The third pitch P3 is roughly half of thesecond pitch P2 between neighboring first masking features 922, 924 inthe first pattern 920. For example, where the first pitch P1 is about200 nm, spacers 935 having a pitch of about 50 nm or less can be formed.

Next, the second pattern 950 provided by the spacers 935 is transferredinto the target layer 110 (not shown). The pattern transfer can beperformed using any suitable etch process selective for the target layer110 relative to the spacers 935. Other details of this step can be asdescribed above with reference to FIG. 3K or 4H. The target layer 110may be further processed to form complete IC devices.

In some embodiments, three dimensional structures can be formed by themethods described above. The three dimensional structures can include,but are not limited to, lines, trenches, vias, pillars, posts, troughs,and moats.

FIGS. 10A-12C illustrate a method of forming an array of isolatedtrenches or vias in a target layer, using anti-spacers in accordancewith some embodiments. In one embodiment, referring to FIGS. 10A and10B, mandrels 1020 extending in the y-direction are formed by, forexample, depositing and patterning a first resist layer on the targetlayer 110, as described above in connection with FIG. 3C. A secondresist layer 1040 is formed over the mandrels 1020 and the target layer110. First anti-spacers 1050 extending in the y-direction are formedaround and on top of the mandrels 1020, thereby defining interveningmask features 1048 extending in the y-direction. The details of thesesteps can be as described above in connection with FIGS. 3D-3G.

Subsequently, the structure shown in FIGS. 10A and 10B is subjected to afreeze step such that the top surface of the second resist layer 1040 ismaintained during a subsequent step. The details of this freeze step canbe as described above in connection with FIG. 3E.

Referring to FIGS. 11A-11C, mandrels 1120 extending in the x-directionare formed by depositing and patterning a third resist layer on thesecond resist layer 1040 in the manner described above in connectionwith FIG. 3C. A fourth resist layer 1140 is formed over the mandrels1120 and the second resist layer 1040. Second anti-spacers 1150extending in the x-direction are formed around and on top of themandrels 1120, thereby defining intervening mask features 1148 extendingin the x-direction. The details of this process can be as describedabove in connection with FIGS. 3D-3G.

Subsequently, the structure shown in FIGS. 11A-11C is subjected todevelopment using a suitable developer. The developer removes the secondanti-spacers 1150, thereby exposing parts of the first anti-spacers 1050and the intervening mask features 1048. Then, the developer furtherremoves the exposed parts of the first anti-spacers 1050, therebycreating an array of holes 1160 defined by the features 1020, 1048,1120, 1148, as shown in FIGS. 12A and 12B. Then, a pattern formed by thearray of holes 1160 is transferred into the target layer 110 in themanner described above in connection with FIG. 3K. The mask features520, 548 are sequentially removed. A resulting structure of the targetlayer 110, which includes an array of isolated holes 1005, is shown inFIG. 12C.

In certain embodiments, the holes 1005 can be filled with a material(e.g., a dielectric material, a conductive material, or a semiconductor)such that structures formed in the holes 1005 can serve as posts orpillars in a resulting electronic circuit. In other embodiments, themethod described above may be adapted for forming isolated holes, e.g.,contact vias or trenches, depending on the design of the electroniccircuit.

In other embodiments, the mandrels 1020 and the intervening maskfeatures 1048 extending in the y-direction can be formed by any of themethods described above in connection with FIGS. 3A-3I, FIGS. 4A-4G,FIGS. 5A-5D, FIGS. 6A-6E, FIGS. 7A-7F, or FIGS. 8A-8E. Then, themandrels 1120 and the intervening mask features 1148 extending in thex-direction can be formed over the mandrels 1020 and the interveningmask features 1048 by any of the methods described above in connectionwith FIGS. 3A-3I, FIGS. 4A-4G, FIGS. 5A-5D, FIGS. 6A-6E, FIGS. 7A-7F, orFIGS. 8A-8E. In some embodiments, a freeze step is required afterforming the mandrels 1020 and the intervening mask features 1048 andbefore forming the mandrels 1120 and the intervening mask features 1148.In other embodiments, no freeze step is required after forming themandrels 1020 and the intervening mask features 1048 and before formingthe mandrels 1120 and the intervening mask features 1148.

FIGS. 13A-15B illustrate a method of forming an array of pillars orposts in a target layer using anti-spacers. In one embodiment, referringto FIGS. 13A and 13B, mandrels 1320 extending in the y-direction areformed by depositing and patterning a first resist layer on the targetlayer 110, as described above in connection with FIG. 3C. Interveningmask features 1348 extending in the y-direction and alternating with themandrels 1320 are formed by forming and removing anti-spacers asdescribed above in connection with FIGS. 3D-3I. Subsequently, a patterndefined by the mandrels 1320 and intervening mask features 1348 istransferred into the target layer 110 in the manner described above inconnection with FIG. 3K. Exposed portions of the target layer 110 areetched, as shown in FIG. 13B, defining elongated trenches or troughs1302 alternating with elongated mesas 1301 (unetched portions) in thetarget layer 110.

Referring to FIGS. 14A-14C, mandrels 1420 extending in the x-directionare formed by depositing and patterning a third resist layer over thetarget layer 110 in the manner described above in connection with FIG.3C. During this step, because the mandrels 1320 and the intervening maskfeatures 1348 have not been subjected to a freeze step, the depositionof the third resist layer wipes the pattern formed by the mandrels 1320and the intervening mask features 1348 (the deposited resist blends withthe existing resist). Subsequently, intervening mask features 1448extending in the x-direction and alternating with the mandrels 1420 areformed by forming and removing anti-spacers in the manner describedabove in connection with FIGS. 3D-3I. A pattern defined by the mandrels1420 and the intervening mask features 1448 is transferred into thetarget layer 110, as shown in FIGS. 15A and 15B, in the manner describedabove in connection with FIG. 3K. Exposed portions of the elongatedtrenches or troughs 1302 of the target layer 110 are etched, as shown inFIG. 15A, defining isolated holes or vias 1303 in the target layer 110.Simultaneously, exposed portions of the mesas 1301 of the target layer110 are etched, defining pillars or posts 1305, as shown in FIG. 15B. Aresulting structure in the target layer 110, which includes an array ofisolated pillars or posts 1305 and isolated holes 1303, is shown in FIG.15C.

In other embodiments, the mandrels 1320 and the intervening maskfeatures 1348 extending in the y-direction can be formed by any of themethods described above in connection with FIGS. 3A-3I, FIGS. 4A-4G,FIGS. 5A-5D, FIGS. 6A-6E, FIGS. 7A-7F, or FIGS. 8A-8E. Then, themandrels 1420 and the intervening mask features 1448 extending in thex-direction can be formed over the mandrels 1320 and the interveningmask features 1348 by any of the methods described above in connectionwith FIGS. 3A-3I, FIGS. 4A-4G, FIGS. 5A-5D, FIGS. 6A-6E, FIGS. 7A-7F, orFIGS. 8A-8E.

Electronic devices, such as IC devices, typically include a plurality ofconductive lines (for example, interconnects) and landing contact padsthat electrically connect the conductive lines to other levels in theIC. The “landing contact pads” may also be referred to as “landing pads”or “contact tabs.” The conductive lines typically have a width narrowerthan the widths of the landing pads. A conventional pitch multiplicationprocess using spacers allows formation of conductive lines having anarrower line-width than that allowed by an available photolithographicprocess. However, because a masking pattern defined by such spacers canonly provide features having such a narrow line-width, it can bedifficult to form larger width landing pads using spacers.

In some embodiments, a process involving anti-spacers may be used tosimultaneously form conductive lines and landing pads integrated withthe conductive lines. Such a process can provide a single maskingpattern for forming pitch-multiplied conductive lines as well as landingpads wider than the conductive lines.

FIGS. 16A-16C illustrate a method of forming conductive lines andlanding pads in an electronic device (for example, an IC circuit), usinganti-spacers in accordance with some embodiments. Referring to FIG. 16A,mandrels 1620 are formed over a target layer 110 that is formed of aconductive material, such as copper, gold, silver, or an alloy thereof.Each of the mandrels 1620 may include a line mask feature 1622 that hasa first width LW1, and a landing pad mask feature 1624 that has a secondwidth LW2. The landing pad mask feature 1624 is connected to one end ofthe line mask feature 1622.

In the illustrated embodiment, the line mask features 1622 of themandrels 1620 extend parallel to one another. In other embodiments, theconfigurations of the line mask features 1622 of the mandrels 1620 canvary, depending on the design of the electronic device formed by themethod. The second width LW2 can be selected, depending on the size of alanding pad to be formed in the target layer 110, and is greater thanthe first width LW1.

In one embodiment, the second width LW2 is about 0.5 to about 5 timesgreater than the first width LW1. The illustrated landing pad maskfeature 1624 has a substantially circular shape, but the skilled artisanwill appreciate the landing pad mask feature 1624 can have various othershapes such as a square shape, a rectangular shape, an oval shape, orthe like, depending on the desired shape of the landing pad. Themandrels 1620 can be formed as described above in connection with FIGS.3A-3C.

Referring to FIG. 16B, intervening mask features 1630 are formed betweentwo neighboring ones of the mandrels 1620 by forming and removinganti-spacers (not shown). Each of the intervening mask features 1630 mayinclude a line mask feature 1632 that has a third width LW3, and alanding pad mask feature 1634 that has a fourth width LW4. The line maskfeatures 1632 of the intervening mask features 1630 extend parallel toone another and to the line mask features 1622 of the mandrels 1620. Inthe illustrated embodiment, the third width LW3 is substantially thesame as the first width LW1, and the fourth width LW4 is substantiallythe same as the second width LW2. In other embodiments, the third widthLW3 can be different from the first width LW1, and/or the fourth widthLW4 can be different from the second width LW2. The intervening maskfeatures 1630 can be formed as described above in connection with FIGS.3D-3I.

In other embodiments, the mandrels 1620 and the intervening maskfeatures 1630 can be formed by any of the methods described above inconnection with FIGS. 4A-4G, FIGS. 5A-5D, FIGS. 6A-6E, FIGS. 7A-7F, orFIGS. 8A-8E.

Referring to FIG. 16C, a cut mask 1650 is provided over the structure ofFIG. 16B. The cut mask 1650 includes an opening 1652 that exposes partsof the landing pad mask features 1634 of the intervening mask features1630 (and optionally end parts of the landing pad mask features 1624 ofthe mandrels 1620) while blocking the other portions of the features1620, 1630. The opening 1652 is shaped such that the landing pad maskfeatures 1634 of the intervening mask features 1630 are electricallyseparated from one another by a subsequent etch process. The exposedparts of the landing pad mask features 1624, 1634 of the features 1620,1630 are removed by any suitable etch process that can remove thematerials of the landing pad mask features selectively relative to thetarget layer 110.

The mask 1650 is removed and the resulting features 1620, 1630 after theetch process are shown in FIG. 16D. A pattern defined by the mandrelsand intervening mask features 1620, 1630 is transferred into the targetlayer 110 in the manner described above in connection with FIG. 3K.

In another embodiment, a pattern formed by the features 1620, 1630 shownin FIG. 16B is first transferred into the target layer 110, and thenlanding pads are defined by another etch step so as to be electricallyisolated from one another. The skilled artisan will appreciate thatvarious modifications can be made to the methods described above,depending on the design of the electronic device.

In the embodiments described above, the landing pads can be formedsimultaneously with conductive lines, thus eliminating separate stepsfor defining and connecting the landing pads to conductive lines. Yet,the pitch of the conductive lines can be reduced at least to the sameextent as in a conventional pitch multiplication process using spacers.While the embodiments above were described in connection with formingconductive lines and landing pads, the skilled artisan will appreciatethat the embodiments can be adapted for forming various other structuresor parts of electronic devices where different shapes or sizes offeatures are formed simultaneously.

In some embodiments, electronic devices, such as arrays in IC's, can bemade by the methods described above. The electronic devices may alsoinclude a system including a microprocessor and/or a memory device, eachof which includes features arranged in an array. Such a system may be acomputer system, an electronic system, or an electromechanical system.

Examples of electronic devices include, but are not limited to, consumerelectronic products, electronic circuits, electronic circuit components,parts of the consumer electronic products, electronic test equipments,etc. The consumer electronic products may include, but are not limitedto, a mobile phone, a telephone, a television, a computer monitor, acomputer, a hand-held computer, a personal digital assistant (PDA), amicrowave, a refrigerator, a stereo system, a cassette recorder orplayer, a DVD player, a CD player, a VCR, an MP3 player, a radio, acamcorder, a camera, a digital camera, a portable memory chip, a washer,a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti functional peripheral device, a wrist watch, a clock, etc.Further, the electronic device may include unfinished intermediateproducts.

Thus, it will be understood that the invention can take the form ofvarious embodiments, some of which are discussed above and below.

In one embodiment, a method of forming features in an electronic deviceincludes forming mandrels defining a first pattern in a first maskinglayer on one or more underlying layers comprising a target layer. Thefirst pattern includes spaces between the mandrels, and has a firstpitch. The method also includes depositing a second masking layer to atleast partly fill the spaces of the first pattern. The second maskinglayer contacts the one or more underlying layers through the spacesbetween the mandrels. The method further includes forming sacrificialstructures to define gaps between at least parts of the mandrels and atleast parts of the second masking layer; and after depositing the secondmasking layer and forming the sacrificial structures, removing thesacrificial structures to define a second pattern having a second pitchsmaller than the first pitch. The second pattern includes the at leastparts of the mandrels and intervening mask features alternating with theat least parts of the mandrels.

In another embodiment, a method of forming features in an electronicdevice includes photolithographically forming mandrels defining a firstpattern in a first masking layer over a target layer. The first patternincludes spaces between the mandrels, and has a first pitch. The methodalso includes depositing a second masking layer to at least partiallyfill the spaces of the first pattern; forming sacrificial structures todefine gaps between at least parts of the mandrels and at least parts ofthe second masking layer; and after depositing the second masking layerand forming the sacrificial structures, removing the sacrificialstructures to define a second pattern having a second pitch smaller thanthe first pitch. The second pattern includes the at least parts of themandrels and intervening mask features alternating with the at leastparts of the mandrels.

In yet another embodiment, a method of forming an integrated circuitincludes forming a first pattern comprising first lines extendingsubstantially parallel to one another in a first direction over a targetlayer. Forming the first pattern includes: providing first mandrels in afirst masking layer over the target layer, the first mandrels havingspaces therebetween; depositing a second masking layer to at leastpartially fill the spaces between the first mandrels; and forming firstsacrificial structures to define gaps between at least parts of thefirst mandrels and at least parts of the second masking layer. Themethod also includes forming a second pattern comprising second linesextending substantially parallel to one another in a second directionover the first pattern, the second direction being different from thefirst direction. Forming the second pattern includes: providing secondmandrels in a third masking layer over the second masking layer, thesecond mandrels having spaces therebetween; depositing a fourth maskinglayer to at least partially fill the spaces between the second mandrels;and forming second sacrificial structures to define gaps between atleast parts of the second mandrels and at least parts of the fourthmasking layer. The method further includes: removing the firstsacrificial structures; removing the second sacrificial structures; andetching the target layer through the first pattern, the second pattern,or a combination of the first and second patterns.

Although this invention has been described in terms of certain preferredembodiments, other embodiments that are apparent to those of ordinaryskill in the art, including embodiments that do not provide all of thefeatures and advantages set forth herein, are also within the scope ofthis invention. Accordingly, the scope of the present invention isdefined only by reference to the appended claims.

What is claimed is:
 1. A method for integrated circuit fabrication, themethod comprising: forming mandrels comprising mandrel material over asubstrate, the mandrels separated by spaces; depositing a fillermaterial into the spaces; forming sacrificial structures along aninterface between the mandrels and the filler material; removing thesacrificial structures to define a mask comprising mask features formedof the mandrel material and the filler material; subjecting the maskfeatures to an etch to round top corners of the mask features; andsubsequently transferring a pattern derived from the mask features tothe substrate.
 2. The method of claim 1, wherein forming the sacrificialstructures comprises chemically altering portions of one or both of themandrels and the filler material along the interface, wherein thechemically altered portions constitute the sacrificial structures. 3.The method of claim 2, wherein chemically altering the portionscomprises diffusing a chemically active species into the portions. 4.The method of claim 3, further comprising depositing the chemicallyactive species on the mandrels before depositing the filler material. 5.The method of claim 5, wherein forming sacrificial structures isaccomplished by diffusing the chemically active species into themandrels before depositing the filler material.
 6. The method of claim2, wherein the filler material comprises a photoresist, whereinchemically altering portions comprises diffusing chemically activespecies from the photoresist to the mandrels.
 7. The method of claim 6,wherein the filler material comprises an acid-based or base-basedchemically amplified resist.
 8. The method of claim 1, wherein maskfeatures formed by the mandrels and mask features formed by the fillermaterial are at different heights after removing the sacrificialstructures, further comprising: etching tops of the mask features formedby the filler material, thereby substantially equalizing the heights ofthe mask features formed by the mandrels and the mask features formed bythe filler material.
 9. The method of claim 1, further comprising:blanket depositing a layer of spacer material conformally over the maskfeatures and the target layer; subjecting the layer of spacer materialto a directional etch to form spacers at sides of the mask features;removing the mask features to leave free standing spacers, wherein thespacers define the pattern transferred to the substrate.
 10. The methodof claim 1, further comprising, after removing the sacrificialstructures: depositing additional masking material into open spacesbetween the mask features; forming additional sacrificial structures atinterfaces between the additional masking material and the maskfeatures; and removing the additional sacrificial structures, whereinthe mask features and a remainder of the additional masking materialform an additional mask pattern.
 11. The method of claim 1, furthercomprising, before subsequently transferring the pattern derived fromthe mask features to the substrate: depositing a protective materialinto the gaps and over the mask features; patterning the protectivematerial to define additional mask features on a level above the maskfeatures; and transferring a pattern defined by the additional maskfeatures to a same level as the mask features.
 12. The method of claim11, wherein removing the sacrificial structures forms gaps, each gapdefining a loop around each mandrel, and wherein: patterning theprotective material exposes ends of the mandrels; and transferring thepattern defined by the additional mask features comprises etching atleast portions of the exposed ends of the mandrels.
 13. The method ofclaim 1, wherein subjecting the mask features to the etch comprisesperforming an isotropic etch.
 14. A method for integrated circuitfabrication, the method comprising: patterning photoresist to formspaced-apart photoresist mandrels over a substrate; at least partiallyfilling spaces between the mandrels with a filler material; reacting oneor both of the mandrels and filler material to form a sacrificialmaterial; selectively removing the sacrificial material to form a maskpattern comprising mask features including the photoresist and thefiller material; rounding top corners of the mask features; andsubsequently transferring the mask pattern to the substrate afterrounding the top corners.
 15. The method of claim 14, further comprisingdepositing a sacrificial layer on the mandrels before depositing thefiller material.
 16. The method of claim 14, wherein transferring themask pattern comprises etching the mask pattern into a hard mask layerbefore etching the mask pattern into the substrate.
 17. The method ofclaim 14, wherein reacting one or both of the mandrels and fillermaterial comprises exposing one or both of the mandrels and fillermaterial to an acid.
 18. A method for integrated circuit fabrication,the method comprising: forming a lower pattern of lines extending in afirst direction, wherein forming the lower pattern comprises: forminglower mandrels comprising lower mandrel material over a substrate, thelower mandrels separated by spaces; depositing a lower filler materialinto the spaces; forming lower sacrificial structures along an interfacebetween the lower mandrels and the lower filler material; and removingthe lower sacrificial structures to define a lower mask comprising lowermask features formed of the lower mandrel material and the lower fillermaterial; and forming an upper pattern of lines above the lower patternlines and extending in a second direction crossing the first direction,wherein forming the upper pattern comprises: forming upper mandrelscomprising upper mandrel material over the first pattern of lines, theupper mandrels separated by spaces; depositing an upper filler materialinto the spaces; forming upper sacrificial structures along an interfacebetween the upper mandrels and the upper filler material; removing theupper sacrificial structures to define an upper mask comprising uppermask features formed of the upper mandrel material and the upper fillermaterial; and aggregating the first and second patterns to form anaggregate pattern in a masking layer; and transferring the aggregatepattern to the substrate.
 19. The method of claim 18, further comprisingsubjecting the lower mask features to an etch to round top corners ofthe lower mask features.
 20. The method of claim 19, further comprisingsubjecting the upper mask features to an etch to round top corners ofthe upper mask features.